As I've mentioned, there is a momento system in place. For those of you unfamiliar with the term and system, momentos are basically spawned as needed NPCs, who will disappear, along with any gear they were carrying, after a certain amount of time. The 'tourists' seen around the mix are the most obvious example of this system in use.
We also have an awesome, versatile and easy to use scripting system in place. I don't know if this can currently be applied to momento NPC, but perhaps with a little tweaking. I'd love to hear from one or more of the coders on this subject.
Assuming said scripting system is, or can be made, compatible with the momento system, adding new life to the dome would be as simple as players submitting scripts and getting them approved, meaning very little extra work on the part of the staff.
Beyond what we've already discussed, there are plenty of options to bring the dome to life. Your average corpie or mixer grabbing a drink at their favorite club, working a shift at the factory, running a random crate, browsing around stores, etc...Add in a few canned responses to common phrases each one might hear and, bam, new life in the dome.
And the beauty of the momento system is once they're gone, they are no longer taking up moo space, so we can see tons of variety, a random mixer or corpie walking down the street that may never be seen again, without taxing the servers too much.
Then again, I might not fully understand said systems, and this is far more difficult than I'm thinking it is.